[FieldTrip] Fwd: Re: band pass and segmentation

"Jörn M. Horschig" jm.horschig at donders.ru.nl
Mon Jul 9 12:17:33 CEST 2012

Dear Ivano,

I am forwarding your message and my reply to the discussion list again, 
so that others might benefit or add information.
What you see looks to me pretty much like a filter artifact, which is 
common to occur at the edges of your signal. In order to reduce these, 
you can think of changing the order of your filter or, more ideal in my 
opinion, use filterpadding. You can either let FieldTrip do that by 
specifying cfg.padding or by defining your trials in a wider range (e.g. 
add 1s pre and post time of interest) and then only plot the time of 
interest, with the knowledge that the 1s padding before and after is 
corrupted by filter artifacts.


-------- Original Message --------
Subject: 	Re: [FieldTrip] band pass and segmentation
Date: 	Mon, 9 Jul 2012 11:01:08 +0100 (BST)
From: 	Ivano Triggiani <ivano_triggiani at yahoo.it>
Reply-To: 	Ivano Triggiani <ivano_triggiani at yahoo.it>
To: 	"Jörn M. Horschig" <jm.horschig at donders.ru.nl>

Hi Jorn,

in attach an example. you can see in the third slide on the right the 
channel that "goes down".

"No man can wear one face to himself
and another to the multitude,
without finally getting bewildered
as to which one is true."

Nathaniel Hawthorne
*Da:* ""Jörn M. Horschig"" <jm.horschig at donders.ru.nl>
*A:* Ivano Triggiani <ivano_triggiani at yahoo.it>; FieldTrip discussion 
list <fieldtrip at science.ru.nl>
*Inviato:* Lunedì 9 Luglio 2012 11:48
*Oggetto:* Re: [FieldTrip] band pass and segmentation

Hi Ivano,

I don't understand your request exactly, could you attach an example 
figure and explain your issue by using that? Then I (or someone else) 
might be able to help you out.


On 7/3/2012 5:42 PM, Ivano Triggiani wrote:
> Hi all,
> I tried to use a simple cfg.bpfilter (0.1 - 40) for an EEG that I 
> divide into 2 secs époques and giving a look it seems that at the 
> board of every window the signal is reduced (just like following a 
> parabolic trend). Is this a problem of the brutal segmentation 
> (respect to a good windowing) or there's something else?
> Ivano
> _______________________________________________
> fieldtrip mailing list
> fieldtrip at donders.ru.nl  <mailto:fieldtrip at donders.ru.nl>
> http://mailman.science.ru.nl/mailman/listinfo/fieldtrip

Jörn M. Horschig
PhD Student
Donders Institute for Brain, Cognition and Behaviour
Centre for Cognitive Neuroimaging
Radboud University Nijmegen
Neuronal Oscillations Group

P.O. Box 9101
NL-6500 HB Nijmegen
The Netherlands

E-Mail:jm.horschig at donders.ru.nl  <mailto:jm.horschig at donders.ru.nl>
Tel:    +31-(0)24-36-68493

Visiting address:
Trigon, room 2.30
Kapittelweg 29
NL-6525 EN Nijmegen
The Netherlands

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